1. Field of the Invention
The present invention relates to safety needle assemblies for safe and convenient handling of needles. More particularly, the present invention relates to a low cost needle assembly having a safety shield.
2. Description of Related Art
Disposable medical devices having piercing elements are typically used for administering a medication or withdrawing a fluid, such as hypodermic syringes, blood collecting needles, fluid handling needles and assemblies thereof. Current medical practice requires that the fluid containers and needle assemblies used in such systems be inexpensive and readily disposable. Safe and convenient handling of disposable medical devices results in the disposal of the medical devices intact.
For example, existing blood collection systems typically employ some form of durable, reusable holder on which detachable and disposable needles and fluid collection tubes may be mounted. A blood collection system of this nature can be assembled prior to use and then disassembled after usage. Thus, these blood collection systems allow repeated use of the relatively expensive holder upon replacement of the relatively inexpensive needle and/or fluid collection tube. In addition to reducing the cost of collecting blood specimens, these blood collection systems also help minimize the production of hazardous medical waste. A blood collection set or intravenous (IV) infusion set typically includes a needle cannula having a proximal end, a pointed distal end and a lumen extending therebetween. The proximal end of the needle cannula is securely mounted in a plastic hub with a central passage that communicates with the lumen through the needle cannula. A thin flexible thermoplastic tube is connected to the hub and communicates with the lumen of the needle cannula. The end of the plastic tube remote from the needle cannula may include a fixture for connecting the needle cannula to a blood collection tube or some other receptacle. The specific construction of the fixture will depend upon the characteristics of the receptacle to which the fixture will be connected.
In order to reduce the risk of incurring an accidental needle-stick wound, protection of used needle tips becomes important. With concern about infection and transmission of diseases, methods and devices to enclose the used disposable needle have become very important and in great demand. For example, needle assemblies commonly employ a safety shield that can be moved into shielding engagement with a used needle cannula without risking an accidental needle stick.
Some needle shields are referred to as tip guards, and include a small rigid guard that can be telescoped along the length of a needle cannula and extended over the puncture tip of the needle for protection. Such conventional tip guard may include some form of tether for limiting the travel of the tip guard to the length of the needle cannula. Additionally, such conventional tip guard typically includes structure that lockingly engages over the tip of the used needle cannula to prevent a re-exposure of the needle. The structure for preventing re-exposure may include a metallic spring clip or a transverse wall integrally formed with one end of the tip guard. Needle assemblies including such tip guards, however, typically include extensive mechanics for positioning of the tip guard, resulting in complex arrangements which are costly to manufacture and assembly. Also, operation of the tip guard can involve substantial manipulation by the user to extend the tip guard to a shielding position.
Accordingly, a need exists for a needle assembly for use with disposable medical devices, such as a blood collection set, which achieves secure and effective shielding of a used needle tip and which is simple and inexpensive to manufacture and easy to operate.